All dating methods have advantages and disadvantages. Sometimes we have no choice since only one method can be
applied to our particular site. However, the more dating methods we can use, the more likely it is that our
timeframe will be reliable.
Any dating method is only possible when the right sort of material is present (for example, there is no possibility
of using radiocarbon or dendrochronology when there is no organic matter or preserved wood available). Scientific
methods are generally comparatively expensive to carry out and also result in damage to the object being dated.
Some (such as archaeomagnetism) can only be carried out on site while the excavation is in progress. Archaeologists
must depend on their experience to guide them as to the most effective use of resources in selecting their dating
methods. Often, this only becomes clear at the post-excavation stage. It is always good practice, therefore, to
take a wide range of samples of any datable material during excavation, so that there will be maximum potential for
a dating programme afterwards. Ideally, materials used should complement each other and provide a means of
cross-checking. Any conclusions drawn from just one unsupported technique are usually regarded as unreliable by
Whatever methods are chosen, the dates we obtain will only be as good as the object selected for dating. 'Residual
finds' are a particular problem. These are objects belonging to an earlier period but present in a later context
due to redeposition. For instance a Romano-British farm of 300AD may be built on the site of an earlier Roman fort
of 100AD. These farmers may disturb finds from the earlier fort while digging ditches or ploughing fields and these
then end up getting reburied in their ditches. If they are then selected for dating the ditch, these finds will
produce a date 200 years too early. This is true whether the object collected is a coin for historical dating, a
bone for radiocarbon dating, a timber for dendrochronology or a pot sherd for thermo-luminescence. Great care must
be taken when selecting materials for dating - for instance badly worn objects may be an indication of long use or
redeposition. It is best to collect as many dates as possible; this will make it easier to see such problems and
therefore make the site timescale more reliable.
Learn more about Radiocarbon, Dendrochronology,
TL and OSL Dating, Historical Dating,
Archaeomagnetic Dating, or return to Chronology.
- C. Renfrew and P. Bahn, Archaeology: Theories Methods and Practice, Thames and Hudson, London 2000, 117-170.